Meteorology

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Met towers for meteorological instruments

Over the past 15 years, we have specialised in the construction of met towers (measurement towers carrying meteorological instruments) so now we are one of the leading suppliers in all of Europe. We work for many of the major wind-turbine manufacturers, installation companies, wind-measurement companies, and energy vendors.

Closely collaborating with major manufacturers and wind-measurement specialists has given us special knowledge and know-how. This is why we can provide our customers with professional advice and service, so they get an ideal solution that meets their needs for good, reliable wind measurements.

Met towers are an important part of building wind farms. The measurement of wind speed, temperature, relative humidity and air pressure are of vital importance to how attractive it is to build a wind farm. Readings are also needed once the wind farm is built, to measure energy produced against prevailing weather conditions.
True measurements are crucial for selecting the right wind turbine for the conditions. There are many instances of where imprecise measurements have had fatal consequences for the success and profitability of a wind farm.

To ensure ideal wind measurements for our customers, we have tested our met tower to determine how far a measurement needs to be taken from the tower to get wind measurements that meet the IEC 61400 norm of a maximum wind-flow distortion of 1%. Therefore, we know exactly how long the booms must be to meet this norm and thus provide our customers with true, reliable measurements.

Temporary or permanent tower
There are a wide variety of met-tower types available, where there is a difference between temporary and permanent met towers.

Permanent met towers are often stand-alone models as they are very strong and can withstand wind and weather. They can be installed for up to 30 years and requirement a minimum amount of maintenance.

Freestanding met towers from Carl C. A/S are designed for heights of up to 200 m. The slim, streamlined design in solid round steel bars ensures minimum impact on wind conditions around the tower, so that readings are as accurate and reliable as possible. The towers are intended to be able to survive extreme weather conditions in coastal areas, or where the ground is flat with no trees or other obstructions. 

Dimensioning and calculating towers from Carl C. A/S are performed by external consulting engineers with extensive experience and expertise within tower construction. Such calculations are made according to norms such as Eurocode, Scandinavian or British standards. The IEC standards are often of major importance to the strength calculations made for met towers.

Carl C. A/S has supplied many met towers for offshore use. The ultra-slim design is the hallmark of met towers from Carl C. A/S. Even very high towers retain an attractive appearance in relation to the monopile foundation they stand on.
The slim construction is also a major advantage when transporting towers to the site, and during erection when space is at a premium.

All our towers have a high quality hot-dip galvanised finish, often with a layer thickness of over 200 µm of zinc. That means long service life, even in an aggressive offshore environment.

Temporary met towers are used in a variety of ways. In some instances, they are installed for a period of three months to three years until the wind turbines are set up, which makes it possible to carry out qualified wind-condition measurements at varying heights. In other instances, they are used to calibrate the wind measurements to make them as accurate as possible. In other words, a mast is set up at the very spot where the wind turbine will stand and then a permanent tower is set up close by. This provides wind measurements from two sites which increases their reliability. When the temporary mast is taken down later on, and the wind turbine is set up at the same location, one knows the exactly effect of the wind on the wind turbine based on the continued measurements from the permanent tower. Large wind farms usually have several measuring positions to enable both up-wind and down-wind measurements. In addition, it a good idea to have several towers located at various places in the farm to be able to compare wind data from several positions and thus optimise turbine output. It is also important that readings are taken at the same height at which turbines produce electricity, as wind speed can vary a lot between different heights.

Carl C. A/S has produced and supplied hundreds of guyedr masts since the company was founded in 1969, including specifically developed masts for taking meteorological readings. A guyed mast is an excellent low-cost solution for temporary reading-taking at heights of between 50 and 200 m. Large-scale investment in wind farms requires thorough measurement of weather conditions in the area. Wind speed and direction, relative humidity, temperature, and air pressure are measured to provide solid data for estimating repayment time.

The B450 guyed mast was developed specially to take meteorological readings for wind farms. It is often used for temporary meteorological stations erected for feasibility studies. The mast is ultra-slim, and held in place solely by the use of guy ropes, ensuring minimum wind distortion. The integrated steps in the mast make it possible to reach the instruments.
The B450 was specially developed being set up by hand, using the mast as a crane. The mast can be assembled vertically piece by piece in 3 m sections to the desired height. This is a major advantage, as many onshore wind farms are often located in remote areas.

The top of our guyed masts can be configured according to individual requirements. A range of standard solutions is available, including a standard 60 mm diameter top rod. Dimensions and design can be customised according to customer specifications.
The standard boom is supplied with a range of different measurement instruments, but can also be custom-configured. The booms are attached to the mast side in the prevailing wind direction, and can be easily retracted for servicing the instruments.  
To protect the instruments in the mast, a lightning rod can be fitted close to the instruments with higher conductivity, conducting lightning past the sensitive instruments. We always recommend protecting masts against lightning strikes. Sooner or later, lightning will strike the mast, and can cause massive damage.